Apparatus using electronically-controlled valves

ABSTRACT

The pumps and pressure controllers described herein aim to pump fluid in two directions, such as from a first port to a second port and vice versa. The pressure controllers aim to control pressure in a system or device, such as a test device, accurately and precisely at a variety of different pressure levels. Generally described, the pumps and pressure controllers described herein may include two or more control valves, which may be actuatable in such a manner so that the pump or pressure controller can switch between operating as a vacuum pump and operating as a compressor. In some embodiments, the pressure controllers may be able to adjust a pressure in the device by small increments thereby providing increased control of the pressure in the device over the prior art. Furthermore, the pressure controllers may be able to control the pressure of a system having low pressure levels.

BACKGROUND

Pumps have been used for centuries for moving fluids, such as liquids,gases, slurries, etc., from a first location to a second location. Pumpscan also operate as compressors or as vacuum pumps when the secondlocation is a closed system, such as a pressure vessel. Pumps have wideapplication. One application for which pumps are employed is a pressurecontroller, which maintains and controls fluid pressure in a device.Generally described, pressure controllers are capable of maintaining oradjusting system pressure levels of an associated system by controllingthe amount of fluid to be added thereto and/or removed therefrom.

Some currently available pressure controllers employ pumps to generatepressure. Such pumps utilize check valves of the ball/spring orpoppet/spring type to preventing fluid flow in the reverse direction.Check valves of the ball/spring type include a ball that is held againsta valve seat by a force from a spring thereby sealing the valve closed.To open the check valve, a pressure force greater than the spring forcemust be applied to move the ball away from the seat. In that regard, thepressure differential required to open the valve, sometimes referred toas the crack or cracking pressure, limits the lowest absolute pressureachievable in the device to be controlled. That is, the device to becontrolled typically cannot be controlled to an absolute pressure levelthat is at or below the pressure required to open the valve.

In general, the rate of flow pumped by piston pumps utilizing checkvalves is controllable by varying the cycle rate of the piston. Thislimits the range of flow rates that may be generated. Pressurecontrollers, however, may need large flow rates to change pressurequickly and at other times may need small flow rates to maintain astable reference pressure. Because of these needs, some pressurecontrollers use piston-pumps with check-valves to generate the largeflow rates and additional control valves to generate small flow rates.The addition of the control valves, however, increases cost, size andweight of the pressure controller.

Furthermore, the device providing precise metering of fluids, e.g. thecontrol valves, is separate from the device generating pressure, e.g.the piston-pump, and thus complicates control of pressure and/or flowrate. For instance, referring to a typical application of a pressurecontroller, wherein the pressure in a device to be controlled iscurrently low and is to be increased to a higher pressure and then heldthere precisely, initially the control valve is opened completely, andthe pump is cycled at full speed. When the desired pressure is near, thepump may be slowed, and the control valve partially closed. If the pumpis slowed too much, however, the pressure between the control valve andthe pump will drop making it difficult to maintain flow through thecontrol valve. If the flow is higher than the desired flow through thecontrol valve, pressure upstream of the control valve will increase tothe maximum pressure of the pump. This consumes excessive power andincreases the required sensitivity of the control valve.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

In accordance with aspects of the present disclosure, a pressurecontroller is provided. The pressure controller comprises a housing thatincludes a first port, a second port, and a cavity. The cavity has avariable volume that expands and contracts during operation of thepressure controller. The pressure controller further includes a firstcontrol valve and a second control valve. The first and second controlvalves have an open state and a closed state. The first control valveselectively connects the cavity in fluid communication with a fluidsource via the first port when the first control valve is in the openposition. The second control valve selectively connects the cavity influid communication with a system to be controlled via the second portwhen the second control valve is in the open position. The pressurecontroller further includes a computing device configured to actuate thefirst control valve and the second control valve between the open andclosed states so as to operate the pressure controller in two modes ofoperation. The first mode of operation is as a compressor configured tosupply fluid from the fluid source to the system, and the second mode ofoperation is as a vacuum pump configured to remove fluid from thesystem.

In accordance with another aspect of the present disclosure, a system isprovided for controlling pressure of a device. The system includes ahousing and a fluid source. The housing has a first port, a second portcoupled in fluid communication with the device, and a cavity connectedin fluid communication with the first port and the second port. Thefluid source is coupled to the first port. The system further includes asystem control valve and a source control valve. The system controlvalve and the source control valve are selectively actuatable to an openposition or to a closed position. Fluid is permitted to flow between thecavity and the second port when the system control valve is in the openposition, and fluid is permitted to flow between the cavity and thefirst port when the source control valve is in the open position. Thesystem further includes a piston, a detector, and a controller. Thepiston is movable in a cylinder for forming the cavity. The cavity hasan increasing volume as the piston moves in a first direction and adecreasing volume as the piston moves in a second, opposite direction.The detector is configured to output one or more signals indicative ofthe piston position as it moves within the cylinder. The controller isconfigured to actuate at least one of the system control valve or thesource control valve to the open position or the closed position basedat least in part on the one or more signals.

In accordance with yet another aspect of the present disclosure, a pumpis provided. The pump includes a first port, a second port, a bore, anda piston. The piston is movable within the bore so as to form a cavityhaving a variable volume. The piston is actuatable within the bore toexpand and contract the volume of the cavity. The pump further includesa first control valve, a second control valve, and a controller. Thefirst control valve is configured to selectively couple the cavity influid communication with the first port when the first control valve isin the open position. The second control valve is configured toselectively couple the cavity in fluid communication with the secondport when the second control valve is in the open position. Thecontroller is configured to actuate the first and second control valvesto the open position or to a closed position as the piston moves withinthe bore so as to cause fluid to flow in a first direction from thefirst port to the second port and a second, opposite direction from thesecond port to the first port.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisdisclosure will become more readily appreciated by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1A is a schematic illustration of one example of a pressurecontroller in accordance with aspects of the present disclosure, whereinthe piston is in a first position;

FIG. 1B is a schematic illustration of the pressure controller of FIG.1A illustrating the piston in a second position;

FIG. 2A is a schematic view of one example of a piston position detectorin a first position in accordance with aspects of the presentdisclosure;

FIG. 2B is a schematic view of the piston position detector of FIG. 2Ain a second position;

FIG. 3 is a block diagram of the pressure controller of FIG. 1A; and

FIG. 4 is another example of a pressure controller formed in accordancewith aspects of the present disclosure.

DETAILED DESCRIPTION

While illustrative embodiments are described below, it will beappreciated that various changes can be made therein without departingfrom the spirit and scope of the claimed subject matter. In that regard,the detailed description set forth below, in connection with theappended drawings where like numerals reference like elements, isintended only as a description of various embodiments of the disclosedsubject matter and is not intended to represent the only embodiments.Each embodiment described in this disclosure is provided merely as anexample or illustration and should not be construed as preferred oradvantageous over other embodiments. The illustrative examples providedherein are not intended to be exhaustive or to limit the disclosure tothe precise forms disclosed. Similarly, any steps described herein maybe interchangeable with other steps, or combinations of steps, in orderto achieve the same or substantially similar result.

The following discussion provides examples of pumps or pumping systems,and systems for controlling pressure, such as pressure controllers, thatmay employ such pumps or pumping systems. Generally described, examplesof the pressure controllers described herein aim to control pressure inan associated system or device, such as a test device, accurately andprecisely at a variety of different pressure levels. In that regard,several examples of the pressure controllers described herein areconfigured to adjust a pressure in the associated device by smallincrements thereby providing increased pressure control as compared toprior art devices. Furthermore, examples of the pressure controllersdescribed herein may be able to control the pressure of an associatedsystem having low pressure levels, such as less than 150 pounds persquare inch (psi). Additionally, examples of the pressure controllersdescribed herein may be able to control a wide range of flow rates andthe direction of the flow.

As will be described in more detail below, examples of the pressurecontrollers and/or pumps described herein may include twoelectronically-controlled valves for regulating fluid pressure, thedirection of fluid flow, and/or the like. In that regard, in someembodiments, the electronically-controlled valves may be controlled insuch a manner as to provide the pressure controller and/or pumps withtwo switchable modes of operation: the first mode of operation being avacuum pump and the second mode of operation being a compressor. In someembodiments, by using electronically-controlled valves, fewer valves maybe used to control the pressure in the associated device to becontrolled.

It will be appreciated that the electronically controlled valves can be“controlled” according to various logic for carrying out the intendedfunction(s) of the pressure controller and/or pump. Examples of logicdescribed herein may be implemented in a variety of configurations,including but not limited to hardware (e.g., analog circuitry, digitalcircuitry, processing units, etc., and combinations thereof), software,and combinations thereof. In circumstances were the components aredistributed, the components are accessible to each other viacommunication links.

Although shown and described for controlling pressure in a system ordevice, it should be appreciated that the examples of the pressurecontrollers and pumps described herein may be applied to other systemswhere pressure control is desired, such as for example, vacuum systemsand fluid flow control systems. Furthermore, it should be appreciatedthat the fluid described herein may include, but is not limited to, aliquid and a gas.

Turning now to FIGS. 1A and 1B, there is shown one embodiment of apressure controller 100 formed in accordance with aspects of the presentdisclosure. As best shown in FIGS. 1A and 1B, the pressure controller100 includes a pump 102 selectively connected to a fluid source 104 anda system 106 to be controlled via first and second electronic controlvalves 110 and 112, respectively. As indicated above, severalembodiments of the pressure controller 100 may function in two modes ofoperation: (1) the first mode being a compressor configured to add fluidto the system 106 from the fluid source 104, thereby increasing thepressure in the system 106; and (2) the second mode being a vacuum pumpconfigured to remove fluid from the system 106 to the fluid source 104,thereby decreasing the pressure in the system 106.

The fluid source 104 can be a tank of liquid, atmospheric air, a supplyof gas under pressure, etc. In that regard, it should be appreciatedthat in some embodiments the fluid source 104 may be a pressurized fluidsource or a source of fluid at atmospheric pressure. In otherembodiments, the fluid source 104 may be at vacuum pressure. Similarly,embodiments of the system 106 may contain a fluid under pressure, atvacuum pressure, or atmospheric pressure, depending on the intendedapplication.

As best shown in FIGS. 1A and 1B, the pump 102 is of the positivedisplacement type, and includes a housing or pump head 116 having acylinder 120, a piston 122 that is reciprocatingly driven in the bore124 of the cylinder 120 via an actuator 128, and first and second ports130 and 132 that are configured to be connected to the fluid source 104and the system 106, respectively. The reciprocating piston 122, inconjunction with the cylinder bore 124, defines a chamber or cavity 136with a variable volume disposed on one side of the piston 122.Operatively connected to the other side of the piston 122 is theactuator 128 for imparting reciprocating movement to the piston 122. Inthe embodiment shown, the cavity 136 is sealed from atmosphere by pistonseal 140, and is selectively connected in fluid communication with thefirst and second ports 130 and 132 via fluid circuit 144 and first andsecond control valves 110 and 112, respectively.

In the embodiment shown in FIGS. 1A and 1B, the actuator 128 comprises arotary-to-reciprocating mechanism in the form of a connecting rod 146and crank 148. The connecting rod 146 is coupled to the crank 148 at afirst end and is coupled to the piston 122 at a second end. A motor 180(FIG. 3) rotates the crank 148 in a counter-clockwise direction as isillustrated in FIGS. 1A and 1B or, alternatively, in a clockwisedirection. As the crank 148 is rotated by the motor, the connecting rod146 causes the piston 122 to move linearly within the cylinder bore 124in a reciprocating manner. In that regard, as the piston 122 moves awayfrom the fluid circuit 144 of the housing 116, the volume of the cavity136 increases, thereby decreasing the pressure therein as is bestillustrated by FIG. 1B. Conversely, as the piston 142 moves towards thefluid circuit 144 of the housing 116, the volume of the cavity 136decreases thereby increasing the pressure in the cavity 136, as is bestillustrated by FIG. 1A.

It will be appreciated that while a connecting rod/crank configurationhas been illustrated as one example of a rotary-to-reciprocatingmechanism, other rotary-to-reciprocating mechanisms can be employed inembodiments of the present disclosure, including cams, Scottish yokes,and the like. Alternatively, embodiments of the present disclosure mayemploy linear actuators, such a hydraulic or pneumatic cylinders, linearmotors, and the like, for driving the piston in a reciprocating manner.While the illustrated embodiment of FIGS. 1A and 1B depict a drivenpiston 122, other embodiments can employ a driven housing 116 with astationary piston to achieve the same or similar affect.

As briefly described above, the pump 102 includes a first control valve110 and a second control valve 112. In the embodiment shown in FIGS. 1Aand 1B, the first control valve 110 is connected in fluid communicationwith the fluid source 104 via the first port 130 and a fluid conduit160, and as such, may be referred to as a source control valve 110.Similarly, the second control valve 112 is connected in fluidcommunication with the system 106 via the second port 132 and a fluidconduit 162, and as such, may be referred to as a system control valve112. As shown best in FIGS. 1A and 1B, the source control valve 110 isconfigured to place the first port 130 in selective communication withthe cavity 136, and the system control valve 112 is configured to placethe second port 132 in selective communication with the cavity 136. Thatis, when the source control valve 110 is in an open position, the fluidcircuit 144 of the housing 116 is in fluid communication with the fluidsource 104, and when the source control valve 110 is in a closedposition, the fluid circuit 144 of the housing 116 is not in fluidcommunication with the fluid source 104. Similarly, when the systemcontrol valve 112 is in an open position, as is best illustrated by FIG.1B, the fluid circuit 144 of the housing 116 is in fluid communicationwith the system 106, and when the system control valve 112 is in aclosed position, the fluid circuit 144 of the housing 116 is not influid communication with the system 106.

It should be appreciated that when the system control valve 112 is inthe open position and the pressure in the cavity 136 is greater than thepressure in the system 106, fluid will flow from the cavity 136 to thesystem 106. If the system 106 is a closed system, then the pump isoperating as a compressor. Conversely, when the pressure in the cavity136 is less than the pressure in the system 106, fluid flows from thesystem 106 to the cavity 136. In that regard, the pump 102 may beoperating as a vacuum pump.

The rate of fluid flow from the cavity 136 to the system 106 may becontrolled based on the timing and/or duration of the opening of thesource control valve 110 and/or the system control valve 112 relative tothe position of the piston 122 in the cylinder 120. For instance, if thepressure controller 100 is operating as a compressor, to obtain maximumflow rates, the source control valve 110 may be opened when the piston122 reaches the end of the compression stroke and the system controlvalve 112 may be opened when the piston 122 reaches the end of theexpansion stroke. Conversely, to obtain small flow rates, the sourcecontrol valve 110 may be opened late in the expansion stroke, and thesystem control valve 112 may be opened late in the compression strongthereby controlling the amount of pressure in the cavity 136. Therefore,the pressure controller 100 is able to control the flow rate to thesystem 106 from a maximum flow rate to a small flow rate. Additionally,the pressure controller 100 may stop flow to the system 106 by notopening the system control valve 112. Furthermore, the source controlvalve 110 and the system control valve 112 may be actuatable forvariable durations and multiple times per pump 122 stroke to control theflow rate through the source control valve 110 or the system controlvalve 112.

It should also be appreciated that the source control valve 110 and thesystem control valve 112 may be any valve actuatable upon receipt ofsuitable signals. Suitable valves include but are not limited tosolenoid valves, pneumatically, hydraulically, or other motor actuatedcontrol valves, piezoelectric control valves, or the like. In theillustrated embodiment, the source control valve 110 and the systemcontrol valve 112 are solenoid valves that comprise a movable valve stem152 and a coil 154. It is to be appreciated that the control valves 110and 112 may have a steady state in the open position and may be actuatedto a closed position in response to receipt of appropriate controlsignals or, alternatively, have a steady state in the closed positionand may be actuated to an open position in response to receipt ofappropriate control signals. In the embodiment shown in FIGS. 1A and 1B,the valves 110 and 112 have a steady state in the closed position, andhave a biased state in the open position. It will be appreciated thatcontrol valves, such as solenoid, piezoelectric, and the like do nothave crack pressures per se, and as such, are able to control pressuresat low pressure levels, such as less than 300 psi, and/or make smalladjustments to the pressure in the system 106 to be controlled.

Referring now to the block diagram of FIG. 3, a computing device in theform of a controller 166, such as a microprocessor, digital circuitry,or the like, is provided for controlling the operation (i.e., opening orclosing) of the control valves 110 and 112 based on movement of thepiston 122. As best shown in FIG. 3, the controller 166 is connected inelectrical communication with a piston position detector 170 and thefirst and second control valves 110 and 112 via one or more drivecircuits 182. Generally described, the controller 166 receives signalsfrom the piston position detector 170 indicative of the position (e.g.,relative or absolute) of the piston 122 as the piston 122 reciprocateswithin the cylinder bore 120. In one embodiment, the piston positiondetector 170 may include two proximity sensors that generate signals ator near the beginning and ending of the piston's stroke. In otherembodiments, the piston position detector 170 may include other sensorsor devices, such as linear or rotary encoders, hall effect transducers,capacitive or inductive transducers, potentiometers, etc., fordetermining the position of the piston. It will be appreciated that theposition of the piston can be also determined by measuring the positionof other components associated with the piston, such as the connectingrod, crank, or the like. As will be explained in more detail below,other embodiments may employ an optical sensor as the piston positiondetector 170.

The controller 166 processes the signals received from the pistonposition detector 170 according to various logic rules, and outputscontrol signals to the one or more drive circuits 182. The one or moredrive circuits 182, in response to receiving control signals from thecontroller 166, process the received control signals, and outputsuitable device level signals (e.g., voltage, current, etc.) to thefirst and second control valves 110 and 112. Upon receipt of the devicelevel signals, the control valves 110 and 112 changes states, such asfrom an open to a closed state or from a closed to an open state. In oneembodiment, the controller 166 may also control the motor 180 of theactuator 128 via an actuator drive circuit 184.

An operation of one embodiment of the pump 102 will now be describedwith reference to FIGS. 1A and 1B. To pump fluid from the fluid source104 to the system 106, the controller 166 operates the control valves110 and 112 in the following manner. As the piston 122 reaches the endof its compression stroke (piston moving from right to left in FIGS. 1Aand 1B), the controller 180 opens the source control valve 110 andcloses the system control valve 112. The control valves 110 and 112remain in such states as the piston 122 moves from the piston positionshown in FIG. 1A to the piston position shown in FIG. 1B. Because thevolume of the cavity 136 is expanding, the pressure therein decreases.If the fluid in fluid source 104 is at a higher pressure, the fluid fromthe fluid source is drawn into the cavity 136. Once the piston 122reaches the end of its expansion stroke (piston moving from left toright in FIGS. 1A and 1B), the controller 166 closes the source controlvalve 110 and opens the system control valve 112. The control valves 110and 112 remain in such states as the piston 122 moves from the pistonposition shown in FIG. 1B to the piston position shown in FIG. 1A.Because the volume of the cavity 136 is decreasing, the pressure thereinincreases. If the pressure in the cavity 136 is greater than thepressure in the system 106, the fluid occupying the cavity 136 is forcedinto the system 106. If the system 106 is closed, the pump 102 will beacting as a compressor.

It will be appreciated that to operate the pump 102 as a vacuum pump(e.g., removing fluid from the system 106), the control valves 110 and112 are operated in the opposite manner as just described. In thatregard, an operation of the pump 102 acting as a vacuum pump will now bedescribed. As the piston 122 reaches the end of its compression stroke(piston moving from right to left in FIGS. 1A and 1B), the controller180 opens the system control valve 112 and closes the source controlvalve 110. The control valves 110 and 112 remain in such states as thepiston 122 moves from the piston position shown in FIGURE lA to thepiston position shown in FIG. 1B. Because the volume of the cavity 136is expanding, the pressure therein decreases. If the fluid in the system106 is at a higher pressure, the fluid from the system 106 is drawn intothe cavity 136. Once the piston 122 reaches the end of its expansionstroke (piston moving from left to right in FIGS. 1A and 1B), thecontroller 166 closes the system control valve 112 and opens the sourcecontrol valve 110. The control valves 110 and 112 remain in such statesas the piston 122 moves from the piston position shown in FIG. 1B to thepiston position shown in FIG. 1A. Because the volume of the cavity 136is decreasing, the pressure therein increases. If the pressure in thecavity 136 is greater than the pressure in the fluid source 104, thefluid occupying the cavity 136 is forced into the fluid source 104. Ifthe system 106 is closed, the pump 102 will be acting as a vacuum pump.

Turning now to FIGS. 2A and 2B, another embodiment of the pistonposition detector 170 will be described. As best shown in FIGS. 2A and2B, the piston position detector 170 includes a light source 172, suchas a light emitting diode (LED), mounted a spaced distance from aphotosensor 174 such that the light source 172 is aligned with thephotosensor 174. The photosensor 174 may be configured to sense a beamof light 176 that emits from the light source 172 as is best illustratedin FIG. 2A. In some embodiments, the photosensor 174 may be coupled to asignal generator.

In the embodiment shown, the light source 172 may be positioned suchthat each time the crank 148 completes a full rotation, a portion of theconnecting rod 146 obstructs the beam of light 176 emitted from thelight source 172 as is best illustrated in FIG. 2B. As the portion ofthe connecting rod 146 obstructs the beam of light 176, the amount oflight sensed by the photosensor 174 is reduced. In response to thisreduction in sensed light intensity, the photosensor 174 may beconfigured to generate a signal for output to the controller 166. In analternative embodiment, the photosensor 174 may be coupled to a signalgenerator configured to generate a signal in response to the reductionin sensed light intensity for output to the controller 166. It should beappreciated that the position of the piston 122 when the portion of theconnecting rod 146 obstructs the beam of light 176 is known based on theknown structure of the pump 102. Therefore, the generated signalcommunicates the position of the piston 122 at the time in which thesignal is generated.

In the illustrated embodiment, the connecting rod 146 obstructs the beamof light 176 emitted from the light source 172 once during each rotationof the crank 148. It should be appreciated that any feature on the crank148 or the connecting rod 146 may be configured to obstruct the beam oflight 176 emitted from the light source 172 and that the obstruction mayoccur any number of times during a cycle.

In addition to determining the position of the piston 122 from theoutput of the piston position detector 170, other operating parameters,such as piston speed, direction, etc., can be obtained. Returning toFIG. 3, in some embodiments, the controller 166 may include or becoupled to a timer 186. In response to receiving the generated signalfrom the piston position detector 170, now referred to as a firstsignal, the controller 166 may be configured to start the timer 186. Asthe crank 148 completes a subsequent rotation, the portion of theconnecting rod 146 again obstructs the beam of light 176 of the pistonposition detector 170 thereby causing the piston position detector 170to generate a second signal for output to the controller 166. Inresponse to receiving the second signal, the controller 166 may beconfigured to stop the timer 186.

Using suitable programmable logic or algorithms, the controller 166 iscapable of determining a rotational speed of the crank 148 or a cyclespeed of the piston 122 based on the first signal and second signal. Thecontroller 166 may be configured to use the determined speed of thepiston 122 and the known position of the piston 122 when a signal isgenerated by the piston position detector 170 to predict a location anddirection of the piston 122 within the cylinder 120 at any given timeduring a subsequent rotation of the crank 148. With this data, thecontroller 166 may be further configured to determine the timing ofcontrol signals for causing the driver circuit 182 to actuate the sourcecontrol valve 110 and/or the system control valve 112 in the desiredsequence, duration, etc.

For example, in one embodiment, depending on the position and directionof travel of the piston 122, the controller 166 alternatingly actuatesthe source control valve 110 and the system control valve 112 from theopen position to the closed position in order to maintain the maximumflow rate through the cavity 136. In another embodiment, depending onthe position and direction of travel of the piston 122, the controller166 alternatingly actuates the source control valve 110 and the systemcontrol valve 112 from the open position to the closed position in orderto maintain and adjust the pressure in the system 106.

It should be appreciated that the duration of which the source controlvalve 110 and/or the system control valve 112 remains open may depend onthe amount of pressure the controller 166 determines appropriate formaintaining or making adjustments to the pressure of the system 106.Small incremental pressure changes may be achieved by opening one orboth of the source control valve 110 and the system control valve 112for only a portion of the expansion and/or compression stroke of thepiston 122. It should be appreciated that the source control valve 110and/or the system control valve 112 may be actuated multiple times withvariable durations during a single cycle of the piston 144 in order toregulate (e.g., maintain or adjust) the pressure in the system 106. Insome embodiments, it may be that the control valves 110 and 112 are openor closed at the same time along a portion of the expansion and/orcompression stroke.

In some embodiments, the pressure controller 100 further includes apressure sensor 190 that is capable of measuring the fluid pressure ofthe system 106, as is illustrated in FIGS. 1A and 1B. The pressuresensor 190 may be coupled to the controller 166 for providing a pressurefeedback signal thereto. In operation, the controller 166 compares thefeedback signal to a desired pressure for the system 106 to identify adifference in pressure. The controller 166 then utilizes the differencein pressure to adjust the control of the control valves 110 and 112.

FIG. 4 is another embodiment of a pressure controller 200 formed inaccordance with aspects of the present disclosure. The pressurecontroller 200 is similar in construction and operation as the pressurecontroller 100 except for the differences that will now be described. Asbest shown in FIG. 4, the pressure controller may include one or moreadditional control valves, such as control valve 214 that connects theport 132 in selective fluid communication with the system 106. Thecontrol valve 214 can be any control valve, including those describedherein, that can be controlled by the controller 166. In operation, thecontrol valve 214 meters the flow of fluid into or out of the system106. Benefits of such an arrangement include, for example, theseparation of the function of pressure control from that of pumping,while being capable of making small incremental pressure adjustments. Inaddition to or instead of control valve 214, a control valve 216 can beemployed for connecting the system 106 to a fluid exhaust/supply 218distinct from the pump 102.

Various principles, representative embodiments, and modes of operationof the present disclosure have been described in the foregoingdescription. However, aspects of the present disclosure which areintended to be protected are not to be construed as limited to theparticular embodiments disclosed. Further, the embodiments describedherein are to be regarded as illustrative rather than restrictive. Itwill be appreciated that variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent disclosure. Accordingly, it is expressly intended that all suchvariations, changes, and equivalents fall within the spirit and scope ofthe claimed subject matter.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A pressure controllercomprising: a housing including a first port, a second port, and acavity, the cavity having a piston that varies a volume of the cavity byundergoing a compression stroke and an expansion stroke during operationof the pressure controller; a first control valve having an open stateand a closed state, the first control valve selectively connecting thecavity in fluid communication with a fluid source via the first portwhen the first control valve is in the open position; a second controlvalve having an open state and a closed state, the second control valveselectively connecting the cavity in fluid communication with a systemto be controlled via the second port when the second control valve is inthe open position; and a computing device configured to actuate thefirst control valve and the second control valve between the open andclosed states so as to operate the pressure controller in two modes ofoperation, the first mode of operation being as a compressor configuredto supply fluid from the fluid source to the system, and the second modeof operation being as a vacuum pump configured to remove fluid from thesystem, wherein the computing device is further configured to sendcontrol signals to the first and second control valves to independentlyopen and close the first and second control valves for one or more timedurations that are less than a time duration equal to complete theexpansion or compression stroke of the piston.
 2. The pressurecontroller of claim 1, wherein the computing device is configured toactuate the first control valve and the second control valve for varyingdurations to provide different flow rates through the second controlvalve.
 3. The pressure controller of claim 2, further comprising apressure sensor configured to measure the fluid pressure of the systemto be controlled, the pressure sensor being coupled to the computingdevice for providing a feedback signal indicative of the pressure in thesystem to the computing device.
 4. The pressure controller of claim 3,wherein the computing device uses the feedback signal to determine whento actuate one of the first control valve and/or the second controlvalve.
 5. The pressure controller of claim 1, further comprising: acylinder defining a bore, wherein: the piston is located in the bore ofthe cylinder; the piston is moveable within the bore so as to change apressure within the cavity; a piston position detector is configured todetect a position of the piston; and the computing device is configuredto control at least one of the first control valve and the secondcontrol valve based at least in part on the position of the piston. 6.The pressure controller of claim 5, wherein the piston moves in the borebetween a first position and a second position in a reciprocatingmanner, and wherein the piston position detector detects the position ofthe piston once per cycle of the piston reciprocating within thecylinder.
 7. The pressure controller of claim 5, wherein the pistonposition detector comprises a light source aligned with a photosensor,and wherein the light source is configured to emit light towards thephotosensor and the photosensor is configured to sense the light emittedby the light source.
 8. The pressure controller of claim 5, wherein thecomputing device is configured to calculate the speed and currentposition of the piston from one or more piston positions detected by thepiston position detector.
 9. The pressure controller of claim 8, whereinthe computing device is configured to control one or more of the firstcontrol valve and the second control valve based at least in part on thespeed and current position of the piston.
 10. The pressure controller ofclaim 1, wherein the first control valve and the second control valveare solenoid valves.
 11. A system for controlling pressure of a device,the system comprising: a housing having a first port, a second portcoupled in fluid communication with the device, and a cavity connectedin fluid communication with the first port and the second port; a fluidsource coupled to the first port; a system control valve that isselectively actuatable to an open position or to a closed position,wherein fluid is permitted to flow between the cavity and the secondport when the system control valve is in the open position; a sourcecontrol valve that is selectively actuatable to an open position or to aclosed position, wherein fluid is permitted to flow between the cavityand the first port when the source control valve is in the openposition; a piston movable in a cylinder for forming the cavity, thecavity having an increasing volume as the piston moves in a firstdirection in an expansion stroke and a decreasing volume as the pistonmoves in a second, opposite direction in a compression stroke; a pistonposition detector configured to output one or more signals indicative ofa position of the piston as the piston moves within the cylinder; and acontroller configured to independently actuate the system control valveand the source control valve between the open positions and the closedpositions for time durations that are less than a time duration equal tocomplete the expansion or compression stroke of the piston.
 12. Thesystem of claim 11, wherein the piston is moveable in the cylinderbetween a first position and a second position, and wherein at least oneof the system control valve or the source control valve is in the openposition for a duration less than an amount of time it takes for thepiston to move from the first position to the second position or viceversa.
 13. The system of claim 11, further comprising an actuatorconfigured to move the piston between a first position and a secondposition, the cavity increasing in volume as the piston moves from thefirst position to the second position and decreasing in volume as thepiston moves from the second position to the first position.
 14. Thesystem of claim 13, wherein the piston position detector includes alight source aligned with a photosensor, and wherein the one or moresignals are generated by the piston position detector in response to aportion of the actuator obstructing a beam of light emitting from thelight source.
 15. The system of claim 14, wherein the piston positiondetector is configured to detect the position of the piston each timethe piston completes one cycle comprising movement from the firstposition to the second position and back to the first position.
 16. Thesystem of claim 11, wherein the piston position detector is configuredto detect a plurality of positions of the piston and generate aplurality of corresponding signals in response to the detected pluralityof positions.
 17. The system of claim 16, wherein the controller isconfigured to determine a speed of the piston based on the plurality ofcorresponding signals.
 18. The system of claim 11, wherein the systemcontrol valve is a first system control valve, the system furthercomprising a second system control valve configured to selectivelycouple the second port to the device.
 19. The system of claim 11,wherein the system control valve and the source control valve aresolenoid valves.
 20. A pump comprising: a first port and a second port;a bore; a piston movable within the bore so as to form a cavity having avariable volume, wherein the piston is moveable within the bore toexpand the volume of the cavity in an expansion stroke and to contractthe volume of the cavity in a compression stroke; a first control valveconfigured to selectively couple the cavity in fluid communication withthe first port when the first control valve is in an open position; asecond control valve configured to selectively couple the cavity influid communication with the second port when the second control valveis in an open position; and a controller configured to actuate the firstand second control valves to the open position or to a closed positionas the piston moves within the bore so as to cause fluid to flow in afirst direction from the first port to the second port and a second,opposite direction from the second port to the first port, wherein thecontroller is further configured to send control signals to the firstand second control valves to independently open and close the first andsecond control valves for time durations that are less than a timeduration equal to complete the expansion stroke or the compressionstroke.
 21. The pump of claim 20, further comprising one or more sensorsconfigured to detect at least a position of the piston and a speed ofthe piston for output to the controller, wherein the controller isconfigured to actuate one or both of the first control valve and thesecond control valve based at least in part on the output of the one ormore sensors.
 22. The pump of claim 20, wherein the controller isconfigured to control the duration in which the first control valve andthe second control valve are in the open position to control the rate offluid flow.
 23. The pump of claim 20, wherein the controller isconfigured to control the timing in which the first control valve andthe second control valve are in the open position based on a position ofthe piston in the bore to control the rate of fluid flow.